Today I stumbled upon this video, from which I got almost fifty year old memories. In those days the early 1970s I did the same, firing wood using a reversed vacuum cleaner melting aluminum (which was my first metal melting experience) and later on coke or anthracite coal which got white hot. Putting a steel bar in the center let it melt. So I used a similar steel 'crucible' as in this video in which the copper indeed melted. It was amazing for me as a highschool boy. But soon I discovered the flaws using steel fake crucibles as the copper attacked the steel and started leaking after a couple of melts. Then I ordered real graphite crucibles which performed much better. A couple of them I still have today and used it just a year ago. By that time I got this book "Foundrywork for the amateur" from a friend and learned a lot from it. https://ia800206.us.archive.org/15/items/Foundrywork_for_the_Amateur/Foundrywork_for_the_Amateur.pdf Now I am lucky to use much better tools and using propane and electric furnace, and hope soon induction becomes affordable for the amateur.
I did the same melting bronze with charcoal in a steel crucible. I couldn't figure out why most of the melt ended up on the floor of the furnace. So I bought two #8 and one #40 silicon carbide crucibles from Budget casting.The #8's both cracked, they were all three Chinese, but the #40 (which is actually a #30) I have been using for seven or eight years. (an obviously different Chinese manufacturer.) It is excellent. I use waste oil now. Solid fuel has its advantages. My charcoal furnace had a ditch-bank clay and sand refractory. It held up well. With gas or oil the refractory takes a beating. Clay/sand would melt on the first firing. Richard
